The present invention relates to installations used for producing artificial cold and more particularly, it relates to absorption lithium bromide refrigerating installations in which high-temperature heat carriers are used as a hot source.
It is known that absorption lithium bromide refrigerating installations operate so that the heat of condensation and absorption is removed with the aid of cooling circulating water. When constructing and using large refrigerating stations the provision thereof with circulating or running cooling water requires considerably high capital and operational investments, and therefore, the problem of the reduction of the amount of the cooling water consumed by absorption lithium bromide installations is rather pressing.
At present, attempts are made to decrease the amount of the circulating water consumed by absorption lithium bromide installations by decreasing the thermal load of the condenser by way of, for example, using a double-stage regeneration and raising the total temperature level of the heat removal by way of, for example, employing cascade systems.
Conventional cascade installations employing high- and low-pressure absorbers and high- and low-pressure evaporators coupled with the latter make it possible to remove the heat of absorption from the installation at a temperature level that is much higher than that in hitherto used installations employing one absorber.
However, in such installations the temperature of the heat removed from the installation is determined in the high-pressure absorber by the temperature of the absorbent at the end of the absorption process in the low-pressure absorber, since it determines the possible limit for the saturation temperature of the vapor formed in the high-pressure evaporator.
With all the other conditions being the same, the temperature of the solution of the absorbent in the low-pressure absorber depends on the temperature of the cold being produced. In view of this the disadvantage of conventional cascade systems is especially important when providing absorption installations for producing cold of zero or negative temperatures, in which the solution of LiBr is to be used as an absorbent.
In installations of a great efficiency it is expedient to cool down the refrigerant by 10.degree.-15.degree. C (for instance, in the case of a group of consumers of artificial cold of initial temperatures differing by 5-7.degree. C).
In this case employment of conventional cascade systems results in considerable losses in the power value of the heat removed from the installation, which is due to a relatively low average temperature level in the high-pressure absorber. At the same time, use of the heat for hot-water supply purposes, or an increase in its temperature level in case the heat is removed directly into air, provides for evident economic advantages.